The hard disk drive (or HDD) to read/write information on a magnetic disk (or disk) employs the disk as a storage medium and read/write data on the disk surface using a magnetic head (or head). The HDD typically comprises a head support device that suspends the head at a predetermined floating height over the disk surface to move the head to a target location on the disk radially.
An example of the head support device with the floating head in a conventional HDD is described as follows with reference to FIGS. 8 and 9. FIG. 8 is a plan view showing the main structure and relation between the head support device and the disk (“disk” also referred to as “recording medium”). FIG. 9 is a perspective view showing the main structure of the head support device in a conventional HDD.
Head support device 91 comprises: comparatively less rigid head suspension (“head suspension” also referred to as “support arm”) 92; plate spring 93; comparatively more rigid base arm 94; slider 95 mounted on the surface of one end of head suspension 92 facing disk 98; and a head (not shown) mounted on slider 95 as shown in FIGS. 8 and 9. Head suspension 92 with comparatively less rigidity is bent to form plate spring 93 at one end, and plate spring 93 is connected to base arm 94. Moreover, base arm 94 is secured rotatably on bearing 96, and head support device 91 can move pivotally within a predetermined angle to a target location on the disk radially using actuator 97 connected to base arm 94. Additionally, head actuator 90 consists of head support device 91, bearing 96 and actuator 97.
Disk 98 rotates at a predetermined speed by disk driving means 99. During a reading/writing operation of the HDD, balance between the floating force by air flow generated during rotation of disk 98 and biasing force against the disk surface suspends slider 95 at a predetermined floating height over the disk surface, and the head mounted to slider 95 reads and/or writes data over the disk surface at a predetermined floating height. Plate spring 93 formed on head support device 91 mainly provides slider 95 with the biasing force against the disk surface. Head support device 91 moves pivotally around bearing 96 as a rotation center using actuator 97 connected to base arm 94 to transport the head mounted on slider 95, floating over the disk surface at a predetermined floating height, to a target track location for reading/writing operation.
In the aforementioned head support device 91, floating at a predetermined height over the disk surface, plate spring 93 provided on head suspension 92 must have a function to allow slider 95 to follow disk 98 steadily under fluctuation of biasing forces caused by product quality fluctuation, in a case of vertical shock of disk 98. Therefore, head suspension 92 has typically a thin-plate or apertured structure with lower rigidity as well as a smaller spring constant to provide head support device 91 with a certain level of flexibility. To withstand and absorb external shocks on slider 95, various methods are presented, such as setting the center-of-mass of head support device on a specific position or adding a counter weight to cancel shocking loads (for example, see Japanese Patent Unexamined Publication No. 09082052 and H11-039808).
However, in the head support device used in conventional HDDs, a vibration mode such as torsion or the like occurs in positioning the head support device to a target track by pivotal movement because of the lowered resonance frequency owe to the adoption of thin-plate structure of head suspension 92. The drawback is that the time necessary to stabilize the vibration mode increases the reading/writing access time.
Additionally, the conventional structure must absorb external shocks by forming an arch in the thin-plate structure. Upon loading strong external shocks on the head support device, therefore, balance between the floating force by air flow generated in rotation of the disk and biasing force against the disk surface is disturbed to cause a possible risk of the slider 95 jumping from the disk surface because rigidity is especially lower in the slider mounting portion of the head suspension. The slider 95 sometimes collides with the disk by strong external shocks causing damages magnetically or mechanically. The problem is commonly observed in disk drives using the floating head system, such as optical disk drive, magneto-optical disk drive or the like.
Moreover, along with the downsizing trend of PCs, small sized and especially low profile HDD is required urgently. A low profile design is, therefore, needed for head support device that is a main component of the hard disk drive.